In some Lego sets, you will come across technic pieces. These can be axles, gears, wheels, liftarms, or 1 x n bricks with holes. The axles fit into the holes on the liftarms, gears, and wheels. The gears can transfer motion to other gears, or other parts.
Beams are basically used to hold cross-axles and other LEGO components together, so they are the framework of most TECHNIC and MINDSTORMS models. There are 2 main types of beam: Straight and Angular. Straight beams are usually found only with circular holes in them while angular beams have a mixture of circular and cross-shaped holes, normally with the cross-shaped ones at either end. The straight beams come in sizes from 2 to 15M. These two groups can then be condensed down again into half-beams, beams and bricks.
Connector pegs are used to hold many LEGO TECHNIC constructions together. There are 3 types of connector pegs:
1) Round Pegs
2) Cross-shaped Pegs
3) Half-half Pegs
The round pegs can be used to connect beams together so that they can both swing freely. The second cross-shaped peg can be used to hold two beams together so that they cannot move, and the last peg can be used to connect a free-spinning beam to a fixed beam. There are also longer versions of the round pegs that can be used to connect multiple beams together. A longer version of the cross-shaped peg is an axle. Some pegs might also be different colours. The black and blue connectors are friction connector pegs, while the other pegs are smooth.
Cross-Axles are cross-shaped rods that can be used to hold wheels, gears beams etc. They are colour coded by their length, even numbered lengths (2M,4M,6M etc) are black while odd numbered lengths (3M,5M,7M etc) are grey. You can place a cross-axle through a circular hole so it can spin freely. This is a handy connection for building with gears and wheels.
A gear is a piece that conveys rotational force to another gear or appliance. The smallest gear in a pair is called the Pinion; the larger gear the gear or the wheel. There are many types of gear that are currently used in LEGO constructions. The common ones are listed below:
Spur Gear – A gear that has radial teeth (teeth that spread from the centre outwards) parallel to the axis
Bevel Gear – A gear that can engage another Bevel gear on a different angle (usually 90 degrees)
Crown Gear - A gear wheel with teeth positioned in the rim at a 90 degree angle to its plane.
Worm Gear - A short rotating screw that meshes with the teeth of another gear.
Rack Gear – A toothed block that another gear can mesh (interlock) with